48 GONADECTOMY IN RELATION TO THE SECONDARY 



that sex, in the sense of the separation of male from female sex cells, may. 

 be determined after fertilization; for example, in normal hermaphro- 

 dites, such as Helix, Lumbricus, etc., and the many instances among 

 plants. Among the latter, many regions that normally produce macro- 

 or micro-spores may, under a suitable stimulus produce the other kind. 

 Neither the assumption of male plumage by the female nor the develop- 

 ment of the accessory reproductive organs need be considered evidence 

 that the female is a suppressed hermaphrodite, because the secretion of 

 the ovary clearly controls their development. On the other hand, it is 

 clearly proven that the female is a suppressed pseudo-hermaphrodite. 



If there is any basis in fact that the normal female is a suppressed 

 hermaphrodite, then, since there is no reason to believe that the male 

 is an hermaphrodite, those avian hermaphrodites that occur in nature 

 must arise through a failure of the mechanism for the suppression of 

 the male in normal females. 



Unless and until ovariotomy should be found to result in actually 

 converting a female into a male with spermatozoa, thus demonstrating 

 that the female is a suppressed hermaphrodite, the effects of castration 

 on the secondary sexual characters can not be said to have a bearing 

 on the problems of sex determination. They demonstrate rather the 

 existence of a mechanism for the control of the secondary sexual char- 

 acters that is so closely associated with certain parts of the mechanism 

 for the determination of sex that the two go together, except, perhaps, 

 in races of the Seabright type. 1 The association, however, throws no 

 new light on the mechanism by which sex is determined, unless we wish 

 to extend the idea of internal secretions by assuming that all individ- 

 uals are hermaphroditic and that at some period after fertilization a 

 mechanism comes into operation that partially or wholly suppresses 

 the opposite sex. It is conceivable that the secretions of certain cells 

 in the embryo may determine which class of primitive ova develops. 

 The result would be the same, of course, as if the usual sex scheme is 

 followed, with this difference, that the determining mechanism is not in 

 itself sex. Such a scheme would account for the appearance of the 

 Miillerian and Wolffian ducts and associated parts in all embryos. 



THE RELATION BETWEEN BREEDING AND GONADECTOMY. 



The results obtained from gonadectomy have considerable bearing 

 of a practical nature on inheritance studies in poultry. We need no 

 longer erect separate categories for characters that appear in one sex 

 only, but may classify a given character in the female with the corre- 

 sponding character in the male, even though the two characters actu- 

 ally appear very unlike. These remarks apply naturally only to those 

 characters that are actually modified by the internal secretion of the 

 ovary, while due regard must be paid to the exceptions noted where 

 the castrated female does not develop a normal male plumage. 



1 See note 2 page 46. 



